1. Field of the Invention
The present invention relates to magnetic field detection, and more particularly concerns solid state magnetic field sensing employing the Hall effect.
2. Description of Related Art
Magnetic sensors or magnetometers have long been used to sense motion and/or position of moving parts, such as, rotating gears or shafts. As use of computers for controlling moving machinery is more widespread, and as electronic sensing and control is more extensively used in controlling operation of moving parts, it becomes increasingly necessary to sense various conditions in the machine so as to provide required inputs to the electronic controls and computers. Automobile engines are one example of complex machines employing computer control that require sensing of various conditions to be provided to a computer that controls operation. Thus, magnetic sensors are employed to sense shaft rotation, rotation of gears, and motions of such automotive components as cam shafts, speedometers, and ignition distribution systems, for example.
A typical magnetometer includes a permanent magnet producing a permanent magnetic field that is disturbed by some part formed of magnetic material that is positioned or moves near the magnetic field. The disturbance of the magnetic field is detected by a magnetic sensor of some type to indicate position or motion of the moving part of magnetic material.
Prior magnetic sensors have employed magneto resistors and reluctance detectors. Sensitivity of such devices is poor, and it is difficult, if not impossible, for such devices to provide good signal output in the presence of low magnetic fields.
Solid state resistors have been employed in various types of sensing arrangements. In one prior sensing system a solid state resistor of relatively large dimensions is subjected to a current flow across the resistor in a first direction so that the presence of a magnetic field directed perpendicular to the plane of the resistor causes a differential voltage at opposite sides of the resistor, in a direction perpendicular to the flow of current and to the magnetic field direction. This differential voltage is a measure of magnetic field magnitude. Again, such sensors have poor sensitivity and do not provide good signals with a low magnetic field. Moreover, the resistor can provide an output indicating only the average of the magnetic field over its entire area so that the relatively large size of the resistor inherently compromises resolution.
Certain materials are known to change resistance in the presence of a magnetic field, and these too have been employed for magnetic sensing, but they are excessively expensive and difficult to manufacture.
Thus, magnetic sensors heretofore available have low sensitivity, relatively low resolution, are large and bulky, and are expensive to manufacture.
Accordingly, it is an object of the present invention to provide magnetic field detection that avoids or minimizes above-mentioned problems.